Effects of retinoic acid on embryonic development of mice in culture

The effects of all-trans-retinoic acid (RA) (tretinoin) on the craniofacial development of mouse embryos were examined using whole embryo culture. In day 8 embryos cultured for 48 h, embryonic growth was inhibited concentration-dependently by all-trans-RA treatment. Most of the treated embryos exhibited hypoplasia of the primary palatal processes and a reduction in the development of the first visceral arches. In day 10 embryos cultured for 48 h, although embryonic growth was not inhibited at any concentrations of all-trans-RA, median cleft lip (93%), hypoplasia of the primary palatal processes (37%) and limb reduction deformities (48%) occurred commonly. Furthermore, RA treatment greatly reduced the size of the secondary palatal processes. The incorporation of 3H-thymidine in the treated maxillary processes was decreased to 65% of the control value at 1.0 x 10(-7) M all-trans-RA. These findings indicate that all-trans-RA is teratogenic in mouse whole embryo culture.     

Effects of retinoic acid on embryonic development of mice in culture

Summary The effects of all-trans-retinoic acid (RA) (tretinoin) on the craniofacial development of mouse embryos were examined using whole embryo culture. In day 8 embryos cultured for 48 h, embryonic growth was inhibited concentration-dependently by all-trans-RA treatment. Most of the treated embryos exhibited hypoplasia of the primary palatal processes and a reduction in the development of the first viscreral arches. In day 10 embryos cultured for 48 h, although embryonic growth was not inhibited at any concentrations of all-trans-RA, median cleft lip (93%), hypoplasia of the primary palatal processes (37%) and limb reduction deformities (48%) occurred commonly. Furthermore, RA treatment greatly reduced the size of the secondary palatal processes. The incorporation of³H-thymidine in the treated maxillary processes was decreased to 65% of the control value at 1.0×10^–7 M alltrans-RA. These findings indicate that all-trans-RA is teratogenic in mouse whole embryo culture.     

Epithelial cell processes in the development of the secondary palate in the mouse.

Ultrastructural studies of palatal shelves of Tuck A mice embryos aged 12.25-14.25 days show discontinuities of the epithelial basement membrane traversed by epithelial cell processes before the onset of midline degenerative changes.     

Thrombocytes et thrombopathies

Summary Preliminary results of a statistical survey of electron micrographs of thrombocytes from 15 patients with haemorrhagic diathesis are reported. The possible significance of ultrastructural changes in relation to factor 3 activity and metabolism deficiency are discussed.     

Muscle lipofuscin content and satellite cell volume is increased after high altitude exposure in humans

Muscle ultrastructural changes during a typical expedition to the Himalayas were analyzed by taking muscle biopsies from seven climbers before and after their sojourn at high altitude (over 5000 m for 8 weeks). M. vastus lateralis samples were analyzed morphometrically from electron micrographs. A quantitative evaluation was made of lipofuscin, satellite cells and myonuclei. Significant increases of the volume densities of lipofuscin (+ 235%) and satellite cells (+ 215%) were observed.     

Muscle lipofuscin content and satellite cell volume is increased after high altitude exposure in humans

Summary Muscle ultrastructural changes during a typical expedition to the Himalayas were analyzed by taking muscle biopsies from seven climbers before and after their sojourn at high altitude (over 5000 m for 8 weeks). M. vastus lateralis samples were analyzed morphometrically from electron micrographs. A quantitative evaluation was made of lipofuscin, satellite cells and myonuclei. Significant increases of the volume densities of lipofuscin (+235%) and satellite cells (+215%) were observed.     

Epithelial cell processes in the development of the secondary palate in the mouse

Summary Ultrastructural studies of palatal shelves of Tuck A mice embryos aged 12.25–14.25 days show discontinuities of the epithelial basement membrane traversed by epithelial cell processes before the onset of midline degenerative changes.     

Thick filament size changes in contraction of human muscles

Summary Measurements done on electron micrographs show that in myofibres with sarcomeres contracted to below 2.1 m, proportional shortening of the A bands occurs. In muscles from patients with idiopathic scoliosis very short A bands are especially prominent.This work was supported by the Muscular Dystrophy Association of America.We wish to thank H. Orgal and Y. Havivi, for their technical assistance, O. Carmi and B. Ghidoni for their help with the measurements and N. Vagenberg for the computer analyses.     

A rapid method for the fractionation of avian blood cell nuclei

Summary Red blood cell nuclei from avian anaemic blood have been fractionated by rate sedimentation on discontinous sucrose gradients into fractions which can be distinguished both by their RNA synthesizing ability and by their morphology as revealed by electron microscopy.Acknowledgment. We wish to thank H. Gitay for the electron micrographs. This work was supported by grants from the University of Cape Town Research Committee and the Council for Scientific and Industrial Research.     

Reinterpretation of the ultrastructure of cartilage matrix.

The epiphyseal cartilage from new-born mouse was treated with collagenase in two ways: either before fixation or after glutaraldehyde fixation. The electron dense granules of the matrix were not seen in the micrographs of cartilage treated with collagenase before fixation. It is concluded that collagen plays a definite role in the formation of the granules at the time of tissue fixation and that the granules are fixation artifacts.     

Surface model of the collagen fibril as determined by two-stage plastic replica

Summary Two-stage plastic replicas of fresh and vacuum dried rat tail collagen were examined by electron microscopy. Microphotometer tracings made from the replica micrographs showed that the surface of the collagen has a periodic undulating topography which includes an approximately 20–40 Å deep depression located within the major band distance.This work was supported by the Hendricks Research Fund No. 93252 and the V. A. Research Service Project No. 098-147718-01.     

Reinterpretation of the ultrastructure of cartilage matrix

Summary The epiphyseal cartilage from new-born mouse was treated with collagenase in two ways: either before fixation or after glutaraldehyde fixation. The electron dense granules of the matrix were not seen in the micrographs of cartilage treated with collagenase before fixation. It is concluded that collagen plays a definite role in the formation of the granules at the time of tissue fixation and that the granules are fixation artifacts.Commonwealth Academic Staff Fellow. Permanent address: Department of Zoology, University of Poona, Poona 411007, India.     

Uterine fluid from progesterone treated rabbits contains subcellular membranes

Summary Uterine fluid from progesterone treated rabbits was shown to be rich in subcellular membrane components consisting of vesicles and cilia-like fragments. In contrast, uterine fluid from untreated does lacked subcellular membranes. Thus, they arise when uterine sperm capacitation ability is suppressed.The assistance of Mr R. Byrne is gratefully acknowledged. Mr K. Bedigian skilfully prepared the electron micrographs. Financial support was received from N.I.H. grant HD 10206-01.     

Mitotic activity in the rat palatal shelves during their fusion in vitro]

Rat palatal shelves explanted on gestational day 15 or 16 are cultivated with their medial-edge epithelial surface in contact. Observations of histological sections showed that, before and during the fusion of the processes, mitotic activity is always lower in the epithelium of the expected fusion zone (EFZ) than in the oral epithelium and progressively decreases during the processus of the fusion.     

Effect of concanavalin A on the palatine ridges in vitro]

Concanavalin A acts in three ways on palatal shelves cultivated in vitro: 1. it has a mitogen effect, particularly on the medio palatal epithelium; 2. this produces thickening of this epithelium; 3. a delayed fusion or no fusion of the palatal shelves. The renewed mitogen activity and loss of adhesion properties seem to be linked.     

Chromatin organization within nuclear blebs in leukocytes ofXenopus laevis

Summary The nuclei from leukocytes of peripheral blood, liver and spleen of an individual anaemicXenopus laevis have been found to possess numerous nuclear blebs or projections. These structures were found to be very variable in size and shape as viewed in electron micrographs, but commonly included an enclosed mass of cytoplasm bound on one side by a very thin section of nuclear material. Such sections are membrane bounded on each side and frequently display an interesting ordered array of chromatin.     

Joint effects of dietary protein levels and vitamin A additions on the induction of cytochrome P450 by DDT in rats]

A 5 P. 100 level of protein from casein in a diet does not allow vitamin A to modify significantly induction of cytochrome P 450 on the Rat receiving or not receiving DDT. When the protein increases to a 15 p. 100 level, the induction is better providing vitamin A is to be given. If protein and vitamin A are necessary for cytochrom P 450 induction, an increase of protein level remains inefficient without vitamin A.     

Maternal vitamin A restriction alters biochemical development of the brain in rats.

The biochemical development of the fetal brain in relation to maternal vitamin A restriction was studied in rats. The vitamin A status of pregnant rats was varied by supplying low, medium and adequate amounts (6, 40, and 100 micrograms retinol/day/kg body weight, respectively) of vitamin A during pregnancy and suckling. The maternal vitamin A restriction caused an altered brain development in terms of tissue weight, DNA, RNA and protein levels, and biosynthesis of DNA and protein from [3H]-thymidine and [3H]-leucine, respectively. A dose-dependent effect of maternal vitamin A restriction on the metabolism of DNA, RNA and protein was noticed in the developing fetal brain of rats.     

Maternal vitamin A restriction alters biochemical development of the brain in rats

Summary The biochemical development of the fetal brain in relation to maternal vitamin A restriction was studied in rats. The vitamin A status of pregnant rats was varied by supplying low, medium and adequate amounts (6, 40, and 100 g retinol/day/kg body weight, respectively) of vitamin A during pregnancy and suckling. The maternal vitamin A restriction caused an altered brain development in terms of tissue weight, DNA, RNA and protein levels, and biosynthesis of DNA and protein from [³H]-thymidine and [³H]-leucine, respectively. A dose-dependent effect of maternal vitamin A restriction on the metabolism of DNA, RNA and protein was noticed in the developing fetal brain of rats.